Need help with ASM disk/diskgroup ghost

I am hoping for a quick answer to this question, as Oracle would
(rightly so) put it as a sev 3 or 4.

Our ASM disks seem to have gotten out of wack (technical term).
We have been running with two disk groups for months. We need to add
an additional disk to the primary disk group.
We had our system administrator add the disk to each node and get it
set up for ASM use.

I tried to add the disk via GRID. It showd as "Member", but not a
member of any group.
I chose it and clicked OK and received the error:
Failed to commit: ORA-15032: not all alterations performed ORA-15033:
disk '/dev/raw/ASM7' belongs to diskgroup "EUDATA_01"

This was news to me, as we should not have a disk group EUDATA_01.

I looked in v$asm_diskgroup and found a new disk group. Further more,
it is listed as group zero! I thought the numbers were sequential and
climbing.

The ASM alert logs don't show anything until the alter to add the disk
to the correct disk group.
At that point, they show my attempts to mount/drop the "new" disk
group.

At this point, I can't drop the disk or disk group. I can't add it
where it needs to be.

Questions:

1) How can I get rid of an un-mountable disk group?
2) How do I pry loose the disk I need to apply to DATA_02?
3) Why don't I see anything in the ASM alert logs?

My versions and such:
I am running a 2 node RAC with ASM. Everything from CRS to the
database is 10.2.0.2. Compatibility was set by a different DBA, so I
don't know why it isn't 10202.
The new disk is /dev/raw/ASM7. The bad disk group is EUDATA_01.